Method and Apparatus Performing Express Forwarding Bypass for Time-Critical Frames

ABSTRACT

A method, apparatus and computer program product for the express forwarding bypass are presented. A timer (NAV) is maintained at each respective node of a wireless LAN, the timer (NAV) set to a corresponding time period during which the respective node must refrain from transmitting on a channel. The first node of said plurality of nodes has a time-critical (TC) frame. The first node detects a frame to be express-forwarded by a second node. The first node decrements the duration field by a first predetermined time increment (DT 0 ) before setting its NAV. The first node attempts transmission of the TC frame or back off countdown when the NAV of said first node expires.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional PatentApplications U.S. Provisional Patent Application No. 60/914,868, filedon Apr. 30, 2007; U.S. Provisional Patent Application No. 60/917,283,filed on May 10, 2007; and U.S. Provisional Patent Application No.60/938,340, filed on May 16, 2007; all of which are incorporated hereinby reference in their entirety.

BACKGROUND

Wireless Local Area Networks (WLANS) have become ubiquitous. Growth indemand for Wireless Local Area Networks (WLANs) is driving thedevelopment of new technology to provide higher throughput. To a greaterextent this growth is due to the increased number of users andapplications desiring wireless transmission and to a lesser extent tothe emergence of new applications needing higher transmission ratesalong a single connection between two points.

In wireless Local Area Networks (LANs), a wireless channel can bereserved for the transmission of a single frame or of a sequence offrames, known as a TXOP (transmit opportunity), while employingasynchronous distributed random channel access methods, as described inthe 2007 802.11 standard, which includes the 11e amendment, where theTXOP was introduced, the IEEE Std 802.11™-2007, (Revision of IEEE Std802.11-1999), and the Wireless LAN Medium Access Control (MAC) andPhysical Layer (PHY) Specifications.

In such an environment, both the source and destination of thetransmission broadcast the reservation duration in order to establishthe interference neighborhood. A TXOP is a sequence of framestransmitted between a pair of nodes following a single contention forthe channel. A TXOP holder, the node initiating the TXOP, may transmitcontention-free after the first transmission to the Responder, which isthe node receiving the frames in the TXOP.

To date, there are two basic ways of reserving the channel for a TXOP inwireless LANs. One method of performing reservation is by utilizingFrame-by-frame reservation. According to the 802.11 distributed channelaccess MAC protocol, RTS/CTS frames are used to notify neighbors of thestart of the reservation. Alternatively, the first frame of a TXOP hasits duration field set to a time interval long enough to reserve thechannel for the transmission of the following frame. The reservationtime is extended on a frame-by-frame basis, by updating the length ofthe reservation with each data frame and the acknowledgement thatfollows. A consequence of frame-by-frame reservation is that, if thereservation is denied, it does not require cancellation.

Another method of performing reservation in wireless LANS is byutilizing Start-to-finish reservation. If it is not be possible toextend the time of channel reservation on a frame-by-frame basis, thechannel must be reserved for the entire sequence of transmissions, startto finish, at the time of the reservation request, and, if thereservation request is denied, or if time remains reserved at thecompletion of transmission, the reservation must be cancelled.

A start-to-finish reservation applies to any combination of nodes (i.e.mesh points/APs/stations). A node reserves a channel to cover an entiresequence of transmissions, directed to either one or various differentdestinations, possibly including responses from the destinations. If thereservation is not authorized, or when the transmission sequence iscompleted, the reserving node releases the remaining reservation time bycanceling the reservation.

To avoid collisions, each node keeps a NAV for a traffic channel, whichis set according to the received reservation requests and responses. ANAV is defined as a time period a node must refrain from transmitting ona traffic channel. It is maintained by each station and is updated bythe Duration field value of received transmissions, which may serve asTXOP reservation requests or responses to reservation requests. Areservation request from the transmissions source is either granted ordenied by the destination, and notice is sent to the source. Theresponse contains in the Duration field the remaining reservationduration in order to notify the neighbors of the destination node.Applications for wireless networks include Voice Over Internet Protocol(VoIP). and multimedia (Voice and/or Video), together referred to asVoIP/multimedia. VoIP/multimedia applications require a certain Qualityof Service (QoS) in order to maintain sufficient quality of thecommunication. Latency can be an issue for VoIP/multi-media. Meeting QoSrequires short total end-to-end over-the-air delays. The 802.11eamendment to the IEEE 802.11 standard, which is incorporated in the 2007revision of the standard, provides mechanisms for reducing theover-the-air delays from transmissions in a wireless LAN. These aresingle hop transmissions. The 802.11e mechanisms may not be adequate formeeting latency requirements in wireless networks involving multiple-hoptransmissions. Wireless mesh networks are such networks. A wireless meshmay be an Ad hoc mode mesh (not attached to a wired network) or aninfrastructure mode mesh (attached to a wired network). In general, bothtraffic with source and destination in the mesh and traffic boundfrom/to a wired network may co-exist on a mesh. The latency/jitter limitfor voice traffic traversing the wired network, in addition to thewireless mesh, is lower (40 to 50 milliseconds) than that for trafficstaying on the wireless mesh (175-200 milliseconds).

A mesh will involve multiple-hop flows. The mesh backbone network is amulti-hop network. The multi-hop path delay will be at least a multipleof the single hop delay. Wireless meshes operating on a single channelhave novel collision behavior that can impact nearby the latencyexperienced end to end, over the air. The prevalence of hidden nodes andthe interaction of contention-based access with multi-hop flows imposelatency increases on both mesh and nearby WLANs beyond what non-meshexperience suggests. Hidden nodes remain hidden after retrial, and theirtransmissions are dropped. The high correlation of sequentiallyforwarded frames on a multi-hop flow cause excessive delays totransmissions that have been involved in a collision. For backwardcompatibility, and for the contention-based access protocol to continueto be used, remedies are needed on the mesh side. For QoS traffic,multi-hop delay must meet the same latency constraints as single-hopdelay. We describe remedies to reduce over-the-air latency. The goal isto reduce the correlated channel contention caused when frames areforwarded for multi-hop flows and reduce the delay experienced by suchflows by forwarding frames along a multi-hop path fast.

SUMMARY

One way to reduce delay in a wireless mesh is by providing capacityprovisioning. The nodes and links of the mesh network must havesufficient capacity to prevent traffic buffer from building up anywherein the network. Proper provisioning involves the use of multiple radiosat nodes of high traffic concentration to match traffic profiles.

Another way to reduce delay in wireless mesh is by providing congestioncontrol. Reducing transmit rate and rerouting traffic can alleviatecongestion, given the provisioning. Even with proper provisioning, thestochastic nature of traffic may produce short-term fluctuations thatmay cause congestion at certain nodes.

MAC layer prioritized transmission of forwarded QoS traffic across themesh helps reduce contention and end-to-end delay along a multi-hoppath, given congestion control and capacity provisioning. Expressforwarding offers prioritized transmission along a multi-hop path. Sinceit gives transmissions along such a path higher priority, it may causetime critical frames, sent typically on a single hop, to be delayed.

Conventional mechanisms such as those explained above suffer from avariety of deficiencies. Embodiments of the invention significantlyovercome such deficiencies and provide mechanisms and techniques thatprovide for express forwarding bypass of frames designated astime-critical frames.

In a particular embodiment of a method for performing express forwardingbypass of time-critical frames, the method includes maintaining at eachrespective node of a plurality of nodes of a wireless LAN, a timer (NAV)set to a corresponding time period during which the respective node mustrefrain from transmitting on a channel. A first node of the plurality ofnodes has a time-critical (TC) frame. The method also includes detectingby the first node of the plurality of nodes, a frame to beexpress-forwarded by a second node. The method further includesdecrementing by the first node the duration field by a firstpredetermined time increment (DT0) before setting its NAV and whereinthe first node attempts transmission of the TC frame or backoffcountdown when the NAV of the first node expires. The method furtherincludes decrementing by a third node, which is the intended recipientof the express-forwarded frame, the duration field by a secondpredetermined time increment (DTI) before setting its NAV and whereinthe third node attempts forwarding of the express-forwarded frame whenthe NAV of the third node expires. DT0 is the increment added to theDuration field value of the express-forwarded frame before it istransmitted by the second node. DTI is shorter than DT0 by at least atime slot.

Other embodiments include a computer readable medium having computerreadable code thereon for providing express forwarding bypass oftime-critical frames. The computer readable medium includes instructionsfor maintaining at each respective node of a plurality of nodes of awireless local area network (LAN), a timer (NAV) set to a correspondingtime period during which the respective node must refrain fromtransmitting on a channel. A first node of the plurality of nodes has atime-critical (TC) frame. The computer readable medium also includesinstructions detecting by the first node of the plurality of nodes, aframe to be express-forwarded by a second node. The computer readablemedium further includes instructions decrementing by the first node theduration field by a first predetermined time increment (DT0) beforesetting its NAV and instructions wherein the first node attemptstransmission of the TC frame or backoff countdown when the NAV of thefirst node expires. The instructions further include decrementing by athird node, which is the intended recipient of the express-forwardedframe, the duration field by a second predetermined time increment (DTI)before setting its NAV and wherein the third node attempts forwarding ofthe express-forwarded frame when the NAV of the third node expires. DT0is the increment added to the Duration field value of theexpress-forwarded frame before it is transmitted by the second node. DTIis shorter than DT0 by at least a time slot.

Still other embodiments include a computerized device, configured toprocess all the method operations disclosed herein as embodiments of theinvention. In such embodiments, the computerized device includes amemory system, a processor, communications interface in aninterconnection mechanism connecting these components. The memory systemis encoded with a process that provides express forwarding as explainedherein that when performed (e.g. when executing) on the processor,operates as explained herein within the computerized device to performall of the method embodiments and operations explained herein asembodiments of the invention. Thus any computerized device that performsor is programmed to perform up processing explained herein is anembodiment of the invention.

Other arrangements of embodiments of the invention that are disclosedherein include software programs to perform the method embodiment stepsand operations summarized above and disclosed in detail below. Moreparticularly, a computer program product is one embodiment that has acomputer-readable medium including computer program logic encodedthereon that when performed in a computerized device provides associatedoperations providing express forwarding as explained herein. Thecomputer program logic, when executed on at least one processor with acomputing system, causes the processor to perform the operations (e.g.,the methods) indicated herein as embodiments of the invention. Sucharrangements of the invention are typically provided as software, codeand/or other data structures arranged or encoded on a computer readablemedium such as an optical medium (e.g., CD-ROM), floppy or hard disk orother a medium such as firmware or microcode in one or more ROM or RAMor PROM chips or as an Application Specific Integrated Circuit (ASIC) oras downloadable software images in one or more modules, sharedlibraries, etc. The software or firmware or other such configurationscan be installed onto a computerized device to cause one or moreprocessors in the computerized device to perform the techniquesexplained herein as embodiments of the invention. Software processesthat operate in a collection of computerized devices, such as in a groupof data communications devices or other entities can also provide thesystem of the invention. The system of the invention can be distributedbetween many software processes on several data communications devices,or all processes could run on a small set of dedicated computers, or onone computer alone.

It is to be understood that the embodiments of the invention can beembodied strictly as a software program, as software and hardware, or ashardware and/or circuitry alone, such as within a data communicationsdevice. The features of the invention, as explained herein, may beemployed in data communications devices and/or software systems for suchdevices such as those manufactured by Avaya, Inc. of Lincroft, N.J.

Note that each of the different features, techniques, configurations,etc. discussed in this disclosure can be executed independently or incombination. Accordingly, the present invention can be embodied andviewed in many different ways.

Also, note that this summary section herein does not specify everyembodiment and/or incrementally novel aspect of the present disclosureor claimed invention. Instead, this summary only provides a preliminarydiscussion of different embodiments and corresponding points of noveltyover conventional techniques. For additional details, elements, and/orpossible perspectives (permutations) of the invention, the reader isdirected to the Detailed Description section and corresponding figuresof the present disclosure as further discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1 a diagram showing the timing of an express forwarded frame amongseveral nodes is shown;

FIG. 2 depicts a flow diagram of a particular embodiment of a method ofperforming express forwarding bypass of time-critical frames; and

FIG. 3 illustrates an example computer system architecture for acomputer system that performs express forwarding bypass fortime-critical frames in accordance with embodiments of the invention.

DETAILED DESCRIPTION

Express forwarding is a technique used to reduce delay for a designatedframe along a multi-hop path by insuring that a forwarding node incursless delay than single-hop transmissions. For a single-channel meshforwarding delay is reduced by reserving the channel for a forwardedtransmission longer, in order to enable the next forwarding node toseize the channel. Immediate access is thus given to nodes, other thanthe first node on a multi-hop path, forwarding QoS traffic.

Express forwarding is a technique used to reduce channel contention anddelay for a designated frame along a multi-hop path by insuring that aforwarding node incurs less delay than single-hop transmissions. For asingle-channel mesh forwarding delay is reduced by reserving the channelfor a forwarded transmission for a sufficiently long time interval toenable the next forwarding node to seize the channel. Immediate accessis thus given to nodes, other than the first node on a multi-hop path,forwarding QoS traffic.

A frame to be express forwarded is designated as a time-sensitive QoS(TSQ) transmission. A special flag may be used to mark a transmission asexpress forwarded, depending on the criteria for a TSQ transmissionand/or the information available along its path. The TSQ designation maybe supplied by the application, for example, a TSQ frame could be aframe of a specified user priority (e.g. VO). Alternatively, the TSQdesignation may also be supplied by the originating node, for example,if there is differentiation between ad hoc and infrastructure traffic,all voice frames starting or destined to the portal would be designatedTSQ by the originating node. The TSQ designation can further be used forother criteria.

In order to process an express forwarded frame, a known time incrementDT0 is added to the value of the Duration field when a TSQ frame isforwarded. The Duration field of the ACK (if any) returned for the TSQframe received at the destination node is set based on the Durationfield of the received frame. All nodes that hear the transmission otherthan the receiving node set their NAV according to the Duration field ofthe received transmission. If the receiving node forwards the frame, itsubtracts DT0 from the Duration value of a received frame before settingits NAV, and attempts transmission of the received TSQ frame whenacknowledgement of receipt of the TSQ frame is complete. DT0 should besufficiently long to enable a forwarding node to process the receivedframe and prepare it for transmission on the next hop. It must be atleast a time slot long.

An alternative (and more efficient) implementation will not add DT0 tothe Duration value of the frame transmitted on the last hop (i.e. to thefinal destination MP).

Referring now to FIG. 1, a diagram 10 showing the timing of an expressforwarded frame among several nodes is shown. Nodes 1-5 are shown, witha three-hop path for an express forwarded frame traversing from node 1to node 2, node 2 to node 3 and then node 3 to node 4. Node 5 is anon-forwarding neighbor node. Each node maintains a NAV for the channel12. A first frame 14 is designated as an express forwarded frame, to beforwarded from node 1 to node 2. The Duration field is set at valuelonger than usual when a frame is transmitted to a forwarding node of amulti-hop path. The forwarding nodes, 2 and 3, transmit sooner. In anembodiment of this invention, the forwarding nodes, 2 and 3, adjust theDuration value on the received frame by subtracting the time intervalDTI when setting their NAV, where DTI is shorter than DT0. Thenon-forwarding neighbor nodes—e.g. node 5—set its NAV by the receivedDuration field. Thus, node 2, as the intended recipient of the forwardedframe does not set its NAV. Accordingly, node 2 will have access tochannel 12 before node 5 does, and the frame will be forwarded morequickly, since node 2 can access the channel before node 5 and forwardthe frame. Thus, node 2 may transmit shortly after transmission andacknowledgment are completed, whereas the NAV at node 5, which was setto the value of the Duration field, has the value DT0 when the receivedframe has been acknowledged.

Contention is reduced when forwarding a TSQ frame for all forwardingnodes other than the first node on path. Neighbor nodes have their NAVstill set to at least one time slot when the new forwarding node isready to transmit (barring any independent NAV-setting request); thusthey will not contend for the channel, letting that node transmit beforeany of them.

A forwarding node may perform Clear Channel Assessment (CCA) beforeattempting transmission. This avoids collisions with another node thathas not heard the received TSQ transmission to set the NAV accordingly.If the channel is busy, the forwarding node backs off a delay from ashort contention window CWmin(EF).

TXOPs allow multiple frames to be transmitted with a single contention.TXOPs can be used together with express forwarding. The combinationreduces contention and collisions along the forwarding path. TheDuration field value on each frame of a TXOP to be forwarded isincreased by DT0. A TXOP may contain exclusively TSQ frames, or a mix offrames, some to be express forwarded and other not. The frames to beexpress forwarded are flagged as TSQ. Preferably the TSQ frames of aTXOP should be transmitted before the non-TSQ frames in order to reducethe processing delay of the TSQ frames at the receiving node and thusenable their immediate forwarding. All TSQ frames in a given TXOP shallbe transmitted to the same node. The Duration field on the ACK (if any)for each of the TXOP frames received at the destination node is setbased on received frame. The receiving node will be able to transmitimmediately following the completion and acknowledgment of the TXOP.Forwarding of the frames in the received TXOP starts when the NAVexpires, which occurs once the entire TXOP has been received andacknowledged. Forwarding of the frames in the received TXOP may involvethe segregation of the frames into different TXOPs according to the nexthop destination node. Frames buffered at the receiving node in the sameaccess category as the received TXOP may be transmitted in the forwardedTXOPs, provided such frames are sent to the same node as the forwardedTXOP and the size of the augmented TXOP does not exceed the TXOP limitfor the access category.

RTS/CTS is the mechanism for reducing the impact of hidden terminals,which are common in a wireless mesh. RTS/CTS protection may be used inconjunction with express forwarding. The combination reduces contentionand collisions on the forwarding path. The RTS of a time-sensitive QoSframe is flagged TSQ and the Duration field on the RTS is increased bythe increment DT0. The node to which the RTS is addressed responds witha CTS with Duration value set based on the Duration field of thereceived RTS. If the node receiving the RTS must forward theRTS-protected frame(s), it does so upon acknowledgement of theRTS-protected frame(s). Forwarding of the received frame or TXOP startswhen the NAV expires, which occurs once the frame or TXOP has beenreceived and acknowledged. The express forwarding mechanism works evenwhen the receiving node is not required to observe its NAV afteracknowledging receipt of a frame. Express forwarding gives priorityaccess to frames marked TSQ over all other traffic.

While express forwarding is used to provide prioritized forwarding ofpackets so designated, there may also be certain frames that are timecritical and require priority over the express forwarded frames. Certainmanagement frames, often sent on a single hop, may require transmissionbefore the express forwarded traffic. In systems utilizing expressforwarding, the express forwarded traffic would delay the transmissionof frames that are not forwarded on a multi-hop path. Express forwardingcan accommodate prioritized channel access for time-critical framesthrough its “bypass” feature.

Nodes with time-critical (TC) frames may gain access to the channelsooner than express forwarded frames as follows. If a node with a TCframe hears a TSQ frame transmitted, it subtracts DT0 from the Durationvalue of a received TSQ frame before setting its NAV, and attemptstransmission or counts down backoff when its NAV expires. Since DT0exceeds DTI by at least one time-slot, a TC frame will be transmittedbefore an express forwarded frame. This does not pose a problem for theexpress-forwarded transmission because the forwarding node performs CCAbefore transmitting. If the channel is busy, the forwarding node backsoff from a short contention window CWmin(EF).

A flow chart of the presently disclosed method is depicted in FIG. 2.The rectangular elements are herein denoted “processing blocks” andrepresent computer software instructions or groups of instructions.Alternatively, the processing blocks represent steps performed byfunctionally equivalent circuits such as a digital signal processorcircuit or an application specific integrated circuit (ASIC). The flowdiagrams do not depict the syntax of any particular programminglanguage. Rather, the flow diagrams illustrate the functionalinformation one of ordinary skill in the art requires to fabricatecircuits or to generate computer software to perform the processingrequired in accordance with the present invention. It should be notedthat many routine program elements, such as initialization of loops andvariables and the use of temporary variables are not shown. It will beappreciated by those of ordinary skill in the art that unless otherwiseindicated herein, the particular sequence of steps described isillustrative only and can be varied without departing from the spirit ofthe invention. Thus, unless otherwise stated the steps described beloware unordered meaning that, when possible, the steps can be performed inany convenient or desirable order.

Referring now to FIG. 2, a particular embodiment of a method 50 ofperforming express forwarding is shown. Method 50 begins with processingblock 52 which discloses maintaining at each respective node of aplurality of nodes of a wireless LAN, a timer (NAV) set to acorresponding time period during which the respective node must refrainfrom transmitting on a channel.

Processing block 54 states wherein a first node of the plurality ofnodes has a time-critical (TC) frame. Certain management frames, oftensent on a single hop, may require transmission before the expressforwarded traffic.

Processing block 56 recites detecting by the first node of the pluralityof nodes, a frame to be express-forwarded by a second node. Expressforwarded traffic would otherwise delay the transmission of that are notforwarded on a multi-hop path.

Processing block 58 discloses decrementing by the first node theduration field by a first predetermined time increment (DT0) beforesetting its NAV. Processing block 60 states the first node attemptstransmission of the TC frame or backoff countdown when the NAV of thefirst node expires. Processing block 62 discloses wherein the firstpredetermined time increment is at least one time slot long. Since DT0exceeds DTI by at least one time slot, a TC frame will be forwardedbefore an express forwarded frame.

Processing block 64 states wherein the first node performs Clear ChannelAssessment (CCA) before attempting transmission. Processing block 66recites wherein when the channel for transmission is busy, the firstnode backs off from a short contention window size for a particularAccess Category.

Processing block 68 discloses when a collision occurs when the firstnode attempts transmission of the time-critical frame when the NAV ofthe first node expires, a random backoff period is observed andretransmission attempted when the backoff period expires.

Processing block 70 states sensing, by the second node with theexpress-forwarded frame, that the channel is busy when the TC frame istransmitted by the first node. Processing block 72 recites wherein inresponse to the sensing the channel is busy, the second node backs offfrom transmitting using a random delay from a short contention window.

Processing block 74 discloses decrementing, by a third node which is theintended recipient of an express-forwarded frame, a duration field by asecond predetermined time increment (DTI) before setting its NAV.Processing block 76 states wherein the third node attempts forwarding ofthe express-forwarded frame when the NAV of the third node expires.Processing block 78 recites wherein the DT1 is shorter than the DT0 byat least one time slot.

FIG. 3 is a block diagram illustrating an example computer system 100 (anode) for implementing express forwarding bypass function 140 and/orother related processes to carry out the different functionality asdescribed herein.

As shown, computer system 100 of the present example includes aninterconnect 111 that couples a memory system 112 and a processor 113 aninput/output interface 114, and a communications interface 115.

As shown, memory system 112 is encoded with express forwarding bypassapplication 140-1. Express forwarding bypass application 140-1 can beembodied as software code such as data and/or logic instructions (e.g.,code stored in the memory or on another computer readable medium such asa disk) that support functionality according to different embodimentsdescribed herein.

During operation, processor 113 of computer system 100 accesses memorysystem 112 via the interconnect 111 in order to launch, run, execute,interpret or otherwise perform the logic instructions of the expressforwarding bypass application 140-1. Execution of express forwardingbypass application 140-1 produces processing functionality in expressforwarding bypass process 140-2. In other words, the express forwardingbypass process 140-2 represents one or more portions of the expressforwarding bypass application 140-1 (or the entire application)performing within or upon the processor 113 in the computer system 100.

It should be noted that, in addition to the express forwarding bypassprocess 140-2, embodiments herein include the express forwarding bypassapplication 140-1 itself (i.e., the un-executed or non-performing logicinstructions and/or data). The express forwarding bypass application140-1 can be stored on a computer readable medium such as a floppy disk,hard disk, or optical medium. The express forwarding bypass application140-1 can also be stored in a memory type system such as in firmware,read only memory (ROM), or, as in this example, as executable codewithin the memory system 112 (e.g., within Random Access Memory or RAM).

In addition to these embodiments, it should also be noted that otherembodiments herein include the execution of express forwarding bypassapplication 140-1 in processor 113 as the express forwarding bypassprocess 140-2. Those skilled in the art will understand that thecomputer system 100 can include other processes and/or software andhardware components, such as an operating system that controlsallocation and use of hardware resources associated with the computersystem 100.

The device(s) or computer systems that integrate with the processor(s)may include, for example, a personal computer(s), workstation(s) (e.g.,Sun, HP), personal digital assistant(s) (PDA(s)), handheld device(s)such as cellular telephone(s), laptop(s), handheld computer(s), oranother device(s) capable of being integrated with a processor(s) thatmay operate as provided herein. Accordingly, the devices provided hereinare not exhaustive and are provided for illustration and not limitation.

References to “a microprocessor” and “a processor”, or “themicroprocessor” and “the processor,” may be understood to include one ormore microprocessors that may communicate in a stand-alone and/or adistributed environment(s), and may thus be configured to communicatevia wired or wireless communications with other processors, where suchone or more processor may be configured to operate on one or moreprocessor-controlled devices that may be similar or different devices.Use of such “microprocessor” or “processor” terminology may thus also beunderstood to include a central processing unit, an arithmetic logicunit, an application-specific integrated circuit (IC), and/or a taskengine, with such examples provided for illustration and not limitation.

Furthermore, references to memory, unless otherwise specified, mayinclude one or more processor-readable and accessible memory elementsand/or components that may be internal to the processor-controlleddevice, external to the processor-controlled device, and/or may beaccessed via a wired or wireless network using a variety ofcommunications protocols, and unless otherwise specified, may bearranged to include a combination of external and internal memorydevices, where such memory may be contiguous and/or partitioned based onthe application. Accordingly, references to a database may be understoodto include one or more memory associations, where such references mayinclude commercially available database products (e.g., SQL, Informix,Oracle) and also proprietary databases, and may also include otherstructures for associating memory such as links, queues, graphs, trees,with such structures provided for illustration and not limitation.

References to a network, unless provided otherwise, may include one ormore intranets and/or the Internet, as well as a virtual network.References herein to microprocessor instructions ormicroprocessor-executable instructions, in accordance with the above,may be understood to include programmable hardware.

Unless otherwise stated, use of the word “substantially” may beconstrued to include a precise relationship, condition, arrangement,orientation, and/or other characteristic, and deviations thereof asunderstood by one of ordinary skill in the art, to the extent that suchdeviations do not materially affect the disclosed methods and systems.

Throughout the entirety of the present disclosure, use of the articles“a” or “an” to modify a noun may be understood to be used forconvenience and to include one, or more than one of the modified noun,unless otherwise specifically stated.

Elements, components, modules, and/or parts thereof that are describedand/or otherwise portrayed through the figures to communicate with, beassociated with, and/or be based on, something else, may be understoodto so communicate, be associated with, and or be based on in a directand/or indirect manner, unless otherwise stipulated herein.

Although the methods and systems have been described relative to aspecific embodiment thereof, they are not so limited. Obviously manymodifications and variations may become apparent in light of the aboveteachings. Many additional changes in the details, materials, andarrangement of parts, herein described and illustrated, may be made bythose skilled in the art.

Having described preferred embodiments of the invention it will nowbecome apparent to those of ordinary skill in the art that otherembodiments incorporating these concepts may be used. Additionally, thesoftware included as part of the invention may be embodied in a computerprogram product that includes a computer useable medium. For example,such a computer usable medium can include a readable memory device, suchas a hard drive device, a CD-ROM, a DVD-ROM, or a computer diskette,having computer readable program code segments stored thereon. Thecomputer readable medium can also include a communications link, eitheroptical, wired, or wireless, having program code segments carriedthereon as digital or analog signals. Accordingly, it is submitted thatthat the invention should not be limited to the described embodimentsbut rather should be limited only by the spirit and scope of theappended claims.

1. A method comprising: maintaining at each respective node of aplurality of nodes of a wireless Local Area Network (LAN), a timer (NAV)set to a corresponding time period during which the respective node mustrefrain from transmitting on a channel, and wherein a first node of saidplurality of nodes has a time-critical (TC) frame; detecting by thefirst node of said plurality of nodes, a frame to be express-forwardedby a second node; and decrementing by said first node the duration fieldby a first predetermined time increment (DT0) before setting its NAV andwherein said first node attempts transmission of said TC frame or backoff contention when said NAV of said first node expires.
 2. The methodof claim 1 wherein said first predetermined time increment is at leastone time slot long.
 3. The method of claim 1 wherein said first nodeperforms Clear Channel Assessment (CCA) before attempting transmission.4. The method of claim 1 wherein when the channel for transmission isbusy, said first node backs off from a short contention window size fora particular Access Category (AC).
 5. The method of claim 1 wherein whena collision occurs when said first node attempts transmission of saidtime-critical frame when said NAV of said first node expires, a randombackoff period is observed and retransmission attempted when saidbackoff period expires.
 6. The method of claim 1 further comprisingsensing, by said second node with the express-forwarded frame, that thechannel is busy when the TC frame is transmitted by said first node. 7.The method of claim 6 wherein in response to said sensing the channel isbusy, said second node backs off from transmitting using a random delayfrom a short contention window.
 8. The method of claim 1 furthercomprising decrementing, by a third node which is the intended recipientof an express-forwarded frame, a duration field by a secondpredetermined time increment (DTI) before setting its NAV.
 9. The methodof claim 8 further comprising wherein said third node attemptsforwarding of said express-forwarded frame when said NAV of said thirdnode expires.
 10. The method of claim 8 wherein said DT1 is shorter thansaid DT0 by at least one time slot.
 11. A computer readable mediumhaving computer readable code thereon for providing express forwardingbypass for time-critical frames, the medium comprising: instructions formaintaining at each respective node of a plurality of nodes of awireless Local Area Network (LAN), a timer (NAV) set to a correspondingtime period during which the respective node must refrain fromtransmitting on a channel, and wherein a first node of said plurality ofnodes has a time-critical (TC) frame; instructions for detecting by thefirst node of said plurality of nodes, a frame to be express-forwardedby a second node; and instructions for decrementing by said first nodethe duration field by a first predetermined time increment (DT0) beforesetting its NAV and wherein said first node attempts transmission ofsaid TC frame or back off countdown when said NAV of said first nodeexpires.
 12. The computer readable medium of claim 11 further comprisinginstructions wherein said first predetermined time increment is at leastone time slot long.
 13. The computer readable medium of claim 11 furthercomprising instructions wherein said first node performs Clear ChannelAssessment (CCA) before attempting transmission.
 14. The computerreadable medium of claim 11 further comprising instructions wherein whenthe channel for transmission is busy, said first node backs off from ashort contention window size for a particular Access Category (AC). 15.The computer readable medium of claim 11 further comprising instructionswherein when a collision occurs when said first node attemptstransmission of said time-critical frame when said NAV of said firstnode expires, a random backoff period is observed and retransmissionattempted when said backoff period expires.
 16. The computer readablemedium of claim 11 further comprising instructions for sensing, by saidsecond node with the express-forwarded frame, that the channel is busywhen the TC frame is transmitted by said first node.
 17. The computerreadable medium of claim 16 further comprising instructions wherein inresponse to said sensing the channel is busy, said second node backs offfrom transmitting using a random delay from a short contention window.18. The computer readable medium of claim 11 further comprisinginstructions for decrementing, by a third node which is the intendedrecipient of an express-forwarded frame, a duration field by a secondpredetermined time increment (DTI) before setting its NAV.
 19. Thecomputer readable medium of claim 18 further comprising instructionswherein said third node attempts forwarding of said express-forwardedframe when said NAV of said third node expires.
 20. The computerreadable medium of claim 8 wherein said DT1 is shorter than said DT0 byat least one time slot.
 21. A computer system comprising: a memory; aprocessor; a communications interface; an interconnection mechanismcoupling the memory, the processor and the communications interface; andwherein the memory is encoded with an express forwarding bypassapplication that when performed on the processor, provides an expressforwarding bypass process for processing information, the expressforwarding bypass process causing the computer system to be capable ofperforming the operations of: maintaining at each respective node of aplurality of nodes of a wireless Local Area Network (LAN), a timer (NAV)set to a corresponding time period during which the respective node mustrefrain from transmitting on a channel, and wherein a first node of saidplurality of nodes has a time-critical (TC) frame; detecting by thefirst node of said plurality of nodes, a frame to be express-forwardedby a second node; and decrementing by said first node the duration fieldby a first predetermined time increment (DT0) before setting its NAV andwherein said first node attempts transmission of said TC frame or backoff countdown when said NAV of said first node expires.